In the production of a polyolefin by a vapor phase polymerization method using a catalyst, poor dispersion of the catalyst is prone to be caused in a vapor phase reaction vessel at the commencement of vapor phase polymerization, and lumps of a polyolefin are prone to be formed due to excessive advance of polymerization at a site where the catalyst concentration has locally become high. If lumps of a polyolefin are formed, then the lumps could occlude a drawing port when drawing the generated polyolefin from the vapor phase polymerization vessel.
As a means for solving such a problem, there is known a method in which a polyolefin powder called “seed powder” is fluidized within a gas phase polymerization vessel before commencing vapor phase polymerization, and then feedstock monomers and a catalyst are fed thereto to commence polymerization (see, for example, Patent Document 1). The seed powder and the catalyst are charged in the vapor phase polymerization vessel due to their friction, etc. and therefore the catalyst is prone to attach to the seed powder due to electrostatic force, and the catalyst attached to the seed polymer is dispersed as the seed powder flows. This is presumed to inhibit the catalyst concentration from locally becoming high and successfully suppress the generation of lumps.